The present invention is related to an electronic glass gob distributor, for glassware article forming machines, or machines for forming thermoplastic article or the like, as well as to an electronic control system to readily and efficiently regulate the movement of the glass gob distributing channels in a programmed sequence and with an exact movement between the several forming stations of the machine.
When manufacturing glass articles or other materials, it is necessary to provide specific doses of melted glass gobs to form certain articles.
These melted glass portions or gobs are obtained from a source containing the melted glass delivered in a continuous stream which is cut intermittently by means of an available controlled cutter, in portions called gobs, which are passed through a gob distributor into one or more cavities on a plurality of the article forming stations, such machines being provided generally with eight article forming stations.
Gob distributors for receiving the gobs from a melted glass stream and feed them into the several forming sections of the machines to manufacture glass articles are very well known and have achieved considerable development in the last years, having brought this type of mechanism to a point of considerable efficiency in units which enable the forming of glass articles in machines of multiple stations, thus increasing the production capacity to a great extent.
The gob distributors known in the former technique comprise generally one or more moving channels, each one of them being supported on a vertical axis, and aligned in such a way that they are moved by means of adequate gear mechanism controlled by a movable cam, which, due to its appropriate design, can make a channel swing at the same time between one glassware forming station and the following station in a specific sequence, duly synchronized by the control cam, in order to obtain the programmed distribution of the gobs from the gob cutter, through the mentioned movable channels towards the corresponding fixed channels in synchronized timing to discharge the gob into the preform station and from this preforming station to the final forming station of the glass article forming machine.
For example, U.S. Pat. No. 3,597,187 to Trudeau issued on Aug. 3, 1971, and assigned to Owens Illinois Inc., and its reissue U.S. Pat. No. Re. 28073 dated July 9, 1974, described apparatus to handle the melted glass molding loads that comprise a pair of curve moving channels, supported on vertical axes that, through appropriate gears, are made to swing by means of a ring gear, mounted on a vertical axis that moves sequentially in a predetermined arc through a transverse spindle which comprises also a cam follower, supported on the control cam, of a specific contour to make the curved channels swing at the same time between one molding station and the following, to discharge the gobs through the fixed channels that carry them to the corresponding preforms in such forming stations. The control cam is controlled to swing by means of a ring gear and a worm screw, which is coupled to a shaft rotatable by means of a synchronized motor which rotates the cam at a constant speed synchronized with the operation controls, for example the timing drum which controls the several operations in each station of a glassware forming machine of glass articles at multiple stations.
U.S. Pat. No. 3,585,017, dated June 15, 1971, to Trudeau, also reveals a device of the same general nature, and it can contain a greater number of channels, for example three, all of them moving at the same time by means of a similar system as shown in U.S. Pat. No. 3,597,187, and its reissue U.S. Pat. No. Re. 28073; such channels being positioned in a block containing a pantograph which keeps the swing of channels from displacing them from their relative positions, in such a form that they are able to swing through the proper angle, preserving their required alignment.
In U.S. Pat. No. 3,721,544, dated Mar. 20, 1973, of Bystrianyk et al, assigned to Emhart Corporation, is also described and claimed a distribution mechanism for gobs for glassware forming machines with multiple cavities and stations, which also comprise essentially a pair of rotating curved channels, each of them being coupled to an indented rack, by means of which they can move at the same time in an angular form from one position to the other of the glassware forming machine, said indented rack being coupled to a common shaft, which at its free end is provided with a cam follower, timed to move by a lever which carries another cam follower supported on a cam, which in this particular case is a horizontal cam, against the vertical cams and with horizontal cam contour as per the Trudeau patents, which in this case performs a function practically identical although by means of another kind of mechanism. The cam in Bystrianyk patent and others, is driven through a transmission that is connected to a synchronized motor causing the cam to swing in synchrony with the operation controls of the diverse forming sections of the machines to manufacture the glass articles.
Finally, U.S. Pat. No. 3,775,083, dated Nov. 27, 1973, to Nebelung et al, assigned to Emhart Corporation, describes and claims a gob distributor for the forming machines of glass articles, which varies in its manner of controlling the movement of the ring gears, timed to move the shafts connected to the moving channels, and at all times in this particular case of the Nebelung's patent and others, such shafts are moved by means of ring gears that are coupled to different racks, each of them being actuated by a linear motor driven by fluid, said motors having a plurality of pistons driven through adequate distances and stopped by adequate stops in such a way that sequential movement can be provided to each one of the motors operated by fluid, in order to enable the mechanism to move the distributor channels between one station and the next one in the sequence, through simple fluid impulses or signals instead of using the traditional cams that were used either by Trudeau or Bystrianyk. Nevertheless, Nevelung and others, use a plurality of individual pistons positioned in tandem in the respective pneumatic cylinders, said pistons being moved individually by means of air signals that are provided from each one of the individual sections of the machine, in order to move the distributing channels in their proper sequence.
The problem encounted due to the use of cams as movable elements to obtain the movement sequences that are required in the distributing channels of a gob distributor for a glassware forming machine, are well known in the art, and reside essentially in the fact that, as the cam is used as a moving element, as was clearly described in the above mentioned U.S. Patents of Trudeau and Bystrianyk and others, such cams suffer considerable wear due to their continuous actuation, which although is very important in a high speed mechanism, must perform in such a way that the cam surface of such cams is readily damaged and because of the wear the distributing channels begin to change their movement, and the moment comes when it is necessary to stop the machine to replace the cam, the variation caused in the position of the distribution channels due to the wear of the cam surface, cause the distribution of the glass gobs to become inefficient in a short period of time. On the other hand the moving cam mechanism, as above mentioned, has the great disadvantage of requiring frequent and accurate maintenance in the fixed channels that receive the glass gobs corresponding to each one of the forming stations, as it is possible that the distributing channels or the fixed channels can be out of alignment very slightly, although a considerable misalignment can occur between such fixed and moving channels of the distributor, with which the distribution of the glass gobs to the several sections of the glassware forming machine becomes also inefficient in the case of such slight misalignment of the channels. On the other hand, these mechanisms operated by a moving cam require that the motor be strictly synchronized with the timing drum of the forming machine of glass articles, inasmuch that if the motor is delayed or advanced there is no way to correct it unless the machine is stopped and required repairs are performed.
Another considerable disadvantage presented by the mechanical control of a moving cam for the gob distributors, resides in the fact that, such controls, based on a mechanical cam, does not provide for any possibility of modification if desired, of the operational sequence of the several sections of the glassware forming machine, unless the cam is replaced by one totally different, which is designed for another sequence, and this, of course, can be done only after stopping the machine to make the cam replacement, such mechanical operation in itself, being very complicated, since the cam is normally covered and it is necessary to disassembled many parts to make the replacement. Finally, with this type of moving cam, it is necessary to operate the gob rejector, in the event that the glass gobs pass to one or more sections of the machine that may be under repair or in the process of changing of molds or similar operations, in a way separated by controls totally different, which should be operated by means of fluid or mechanical signals totally different which constitutes another serious disadvantage of this kind of moving cam mechanisms.
Even though the control mechanism of the Nebelung et al U.S. Pat. No. 3,775,083 eliminates totally the use of a moving cam to control the moving channels and movement of the glass gob distributor; instead, a considerable complexity is incorporated to the mechanism, whereby the provision and construction of a plurality of individual pistons is required, all of them being placed in tandem and abutting one against the other in a predetermined sequence, in order to make the staged and sequential movements of the distribution channels, so that the complexity in the mechanism causes continuous failures and makes the fluid control highly inefficient, and mainly for high speed performance such as required in the glassware forming machines.
In this particular case an additional signal of the several glassware forming stations for the forming machines of is also required, to provide for rejection in the event that one of the sections is in repair or the mold is being replaced.
Upon carefully analyzing the failings in the prior art devices and all of these problems, herein enumerated, Fabricacion de Maquinas, S. A., a Mexican company, located at Guerrero Norte No. 3200, Monterrey, Nuevo Leon, Mexico, designed and built a hydraulic control mechanism for a gob distributor in glassware forming machines, in which the rotary channels of the gob distributor were engaged to respective gears, which were synchronized by means of a rack coupled to a hydraulic system, including a hydraulic servomechanism which provides all the movement control, and the hydraulic servomechanism followed a control cam that provided the angles of the movement, times of stop, acceleration and deceleration of the system, and including the distribution channels of the melted glass gob distributor. In that way, the cam that traditionally had been used as a moving element, as per the former description, with regard to the Trudeau and Bystrianyk and other patents, this particular system is used only as a control element that was not exerting any considerable effort, since the effort was exerted by the hydraulic system itself when moving the total gearing and the distribution channels, and, therefore as this was a semihydraulic system operating at high speed, it achieved much better responses and more precise than the previously described mechanical systems, and furthermore, the endurance of the cam was much longer, and had less problems in regard to the type of maintenance required. Nevertheless, this system proved to be inefficient at low speed, since it presented serious adjusting and maintenance problems, in addition that normally, the hydraulic systems require certain amount of care in operation.